In structural engineering, one of the design criteria is the need to maintain structures safety and functionality conditions throughout their useful life. This way, several structural health monitoring methodologies (SHM) have been developed. This evaluation occurs through the continuous sensing of structures in order to validate their behavior over time. Dynamic response can be considered a gradually explored methodology as SHM. In-service structures tend to suffer with vibrations that produce a dynamic response. The existence of structural damage produces a degradation of properties such as mass and stiffness, resulting in variation of modal properties such as natural frequencies, vibration modes and damping. In the present research, with the aid of a duly validated finite element model, it is proposed a damages diagnosis methodology through experimental modal parameters. The proposal will be through the comparison of numerical responses and dynamic tests results made with a damaged slab. The analysis aim to estimate the structure s stiffness variation, which corroborates the alteration of the dynamic parameters. Phenomena such as breathing cracks, where the fissure is open or closed at different times during the vibration, will also be evaluated. In addition, the effect of concrete stiffening around the cracked region will be considered. These processes considerably affect the stiffness of the cracked element. In this way, the objective is a robust model for the analysis of cracked reinforced concrete slabs from the analysis of their dynamic behavior.